Hydrogen assisted combustion

ABSTRACT

An apparatus for feeding hydrogen into an intake ( 11 ) of an engine ( 1 ), including: an air inlet ( 23 ); a hydrogen inlet ( 21 ); a mixing chamber ( 20 ) for generating a fuel mixture from hydrogen and air introduced from the inlets, the chamber being adapted to couple to the intake of the engine, for introducing the fuel mixture thereto; and control means ( 26 ) for controlling airflow through the mixing chamber. The control means may include an air speed control for varying an effective cross-section of air flow through the apparatus. The air speed control is preferably in the form of an annular collar arranged in the chamber for radial expansion or contraction.

FIELD OF THE INVENTION

[0001] The present invention relates to hydrogen assisted combustionparticularly, but not exclusively, for a diesel engine.

BACKGROUND OF THE INVENTION

[0002] It is known to use hydrogen as a fuel additive in internalcombustion engines, however, relatively little work appears to have beencarried out on application of hydrogen assisted combustion tocompression ignition engines such as diesel engines.

OBJECT OF THE INVENTION

[0003] The present invention seeks to provide an apparatus suitable forachieving workable hydrogen assisted combustion in a diesel engine.

SUMMARY OF THE INVENTION

[0004] In accordance with the invention, there is provided an apparatusfor feeding hydrogen into an intake of an engine, including:

[0005] an air inlet;

[0006] a hydrogen inlet;

[0007] a mixing chamber for generating a fuel mixture from hydrogen andair introduced from the inlets, the chamber being adapted to couple tothe intake of the engine, for introducing the fuel mixture thereto; and

[0008] control means for controlling airflow through the mixing chamber.

[0009] Preferably, the apparatus further includes a water inlet forintroducing atomised water into the fuel mixture.

[0010] Preferably, the apparatus further includes a temperature controldevice for controlling temperature of the air passing through the mixingchamber.

[0011] Preferably, the apparatus further includes a density controlassembly for controlling density of the air entering the mixing chamber.More preferably, the assembly includes a Venturi intake.

[0012] The control means preferably includes an air volume control whichmay be in the form of a butterfly valve, positioned between the chamberand the air inlet.

[0013] The control means may also include an air speed control forvarying an effective cross-section of air flow through the apparatus.The air speed control is preferably in the form of an annular collararranged in the chamber for radial expansion or contraction. The annularcollar may, for example, be in the form of an expandable bladder.

[0014] The chamber preferably includes an annular cage arranged to limitinward expansion of the collar so as to maintain at least a minimumcross-section of air flow through the chamber.

[0015] Preferably, the apparatus includes mixing fins to enhanceturbulent air flow within the chamber. The mixing fins may be connectedto the cage, within the chamber.

[0016] Preferably, the apparatus also includes an electrolysis cell orplasma arc or other means for dissociating water into hydrogen andoxygen gas, for introduction into the mixing chamber.

[0017] In another aspect, there is provided a combustion ignition engineincluding an apparatus as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The invention is more fully described, by way of non-limitingexample only, with reference to the accompanying drawings, in which:

[0019]FIG. 1 is a schematic representation of an engine with anapparatus of the invention;

[0020]FIG. 2 is a cross-sectional view of the apparatus of FIG. 1;

[0021]FIG. 3 is a cross-sectional view of the apparatus with a modifiedchamber construction, shown in a first condition;

[0022]FIG. 4 is a cross-sectional view of the chamber taken along theline a density control assembly for controlling density of the airentering the mixing chamber; shown in FIG. 3;

[0023]FIG. 5 is a view similar to that of FIG. 3 with the chamberconstruction shown in a second condition; and

[0024]FIG. 6 is a cross-sectional view of the chamber, taken along theline an air volume control, shown in FIG. 5.

DETAILED DESCRIPTION

[0025] An engine 1 is schematically represented in FIG. 1 by an enginecylinder 2, which houses a piston 3 and defines a combustion region 4into which a liquid fuel is injected, as illustrate by arrow 5, forcombustion and expansion, to drive the piston, and subsequent exhaustthrough outlet pipe 6.

[0026] Apparatus 10 is coupled to an intake 11 of the cylinder 2 toprovide an oxygen/hydrogen fuel mixture to assist in combustion of theliquid fuel. The apparatus 10 includes an electrolysis cell 12 whichreceives H₂O from a water input 13 for dissociation into constituentgases H₂ and O₂, which are fed into a feed line 14. The feed line 14includes a flash back preventer 15, through which the H₂ and O₂ gasespass to be introduced into a mixing chamber 20 via a hydrogen inlet 21.The mixing chamber 20 is also arranged to receive steam or water, inatomised form, from a water inlet 22 and air from an air inlet 23.

[0027] A more detailed view of the apparatus 10, excluding the feed line14, can be seen in FIG. 2. The apparatus is shown as including a densitycontrol 24, such as a Venturi intake, a temperature control device 25,such as a reverse-cycle heat exchanger, and control means 26 forcontrolling air flow through the chamber 20. Mixing fins 27, 28 are alsoprovided to increase turbulence within the chamber and enhance mixingbetween atomised water and hydrogen from the inlets 22 and 21,respectively, and air travelling through from the air inlet 23.

[0028] In the arrangement shown, the control means 26 comprises a volumecontrol 27, in the form of a butterfly valve 28, which allows the totalvolume of air passing through the mixing chamber to be varied, as enginedemand varies. However, the control means 26 may also include an airspeed control 30 which is shown in the apparatus of FIGS. 3 to 6, wherelike parts are denoted with like reference numerals.

[0029] The air speed control is in the form of an annular collar 31which is coaxially housed within the chamber 20 for radial expansion orcontraction, so as to vary the cross-section, and thereby the speed, ofair flow through the chamber. For that purpose, the collar may beconstructed of a bladder 32 which is expandable from a first condition,as shown in FIGS. 3 and 4, to a second, expanded condition as shown inFIGS. 5 and 6. To move from the first to the second condition, thebladder may be coupled to a pressure supply input 33, which may, forexample, be controlled by feedback from the engine speed or directly bya velocity measuring probe at a discharge end of the chamber.

[0030] The provision of the bladder 32 thereby allows the effectiveinternal diameter of the mixing chamber to maintain an optimum velocityof air through the chamber at all engine speeds. For example, at lowengine speeds (rpm) the chamber needs to have a relatively smalleffective diameter to get a small volume of air, as required by theengine, up to a desired velocity, whereas the chamber needs to have arelatively large diameter to maintain the same air velocity when the airvolume required by the engine is much higher. As such, the bladder needsto be inflated during low engine speeds and deflated at high enginespeeds. It has been found that varying the effective diameter of themixer in that manner enables high mixing efficiencies to be maintainedsuch that the amount of hydrogen added to the air flow can be reduced tohalf or a third that otherwise required, whilst still maintaining apower enhancing effect on the engine to reduce liquid fuel consumption.By way of example, in one experiment it was found that 17% hydrogen byvolume of air was required for relatively low air velocity(approximately 15 m/s) in order to reduce the fuel consumption of dieselby 40%. At high velocities, however, (approximately 30 m/s) only 5%hydrogen by volume of air was required to reduce the liquid fuelconsumption by 50%.

[0031] An annular cage 34 is also provided within the chamber 20 tolimit radial expansion of the bladder 32 and ensure at least a minimumcross-section of air flow through the chamber is maintained. Mixing fins35 project inwardly of the cage 34 so as not to interfere with operationof the bladder 32.

[0032] As may be appreciated from the above, the apparatus 10 allows forcontrol of each major parameter to allow for optimisation of volume,speed and mixing ratios of hydrogen, oxygen, water/steam and air passingthrough the mixing chamber to ensure maximum efficiency in power outputof the engine whilst minimising the liquid fuel consumption. A briefdescription of each of the relevant parameters is as follows:

[0033] 1. Air Speed.

[0034] The effective diameter of the mixing chamber has to be sized tomatch the engines optimum performance speed. At the optimum speed, thevelocity within the mixer has to be such that the particles of waterentrained into the airflow from inlet 22 stay in their atomised form,and do not have time to merge with other atomised droplets before beingaspirated from the mixing chamber 20 into the engine cylinder 2. Theoptimum velocity required, from experiments conducted on various enginesto date, is in the range of between 15 and 20 meters per second withinthe mixer. The highest efficiency that has been recorded repeatedly isat 17 m/s. With current testing the engine efficiency rises withvelocity up to 17 m/s, then starts to taper off as the velocitycontinues to increase, to the point where the efficiency of 20 m/s isabout that of 15 m/s. As the velocity rises over 20 m/s, the efficiencycontinues to fall as if the engine is starving for air.

[0035] So with the current mixer configuration, the optimum velocityrange is between 15 and 20 m/s to premix the atomised water, thehydrogen gas and the oxygen gas. With the same fuel, air, water andgases ratio going through the mixer, there was up to a 70% increase inuseable engine output comparing 10 m/s to 17 m/s velocity through themixer. So less hydrogen is needed to be added to have the same reductionin fuel consumption if the velocity is optimised.

[0036] Air speeds outside the above range can also be realised bychanging the inner diameter of bladder. For example, for a deliverytruck, the normal range of diesel engine speed is from 1000 rpm to 3000rpm and the effective diameter of the mixer may therefore be adjustedacross the rev range. However, for a line-haul truck engine which spendsmost of its operating life in a fairly narrow rev range, with gearchanges taking the speeds up and down, the effective diameter size ofthe chamber may be set for the higher end of the engine's running speed,with a fuel efficiency compromise at lower speeds or idle. Similarly,for constant speed engines such as generators and pumps, the diameter ofthe mixing chamber may be sized and fixed to optimise the exact enginespeed.

[0037] 2. Turbulence.

[0038] The length of the mixer needs to be sufficient to set upturbulent air flow and will be proportional to the optimised effectivediameter of the chamber. The mixing fins are ideally provided bothupstream and downstream of the gas and water inlets 21, 22 to enhancethe turbulent flow.

[0039] 3. Air Volume.

[0040] The quantity of air passing through the chamber, as controlled bythe butterfly valve 28, allows for the engine to be choked, if required,to increase the vacuum on the mixing chamber 20. The valve thereforeprovides an important function of preventing the engine fromoverspeeding when load is removed and before a fuel rack has had achance to respond and reduce the amount of liquid fuel being injectedinto the cylinder 2. In the absence of the volume control 27, the enginewould rapidly accelerate, with no load applied, which would have thepotential of damaging the engine.

[0041] 4. Atomisation of Water.

[0042] There are three main advantages derived from adding water to thefuel mix:—1) Stable ignition, no pre-ignition; 2) Lowering of the oxidesof nitrogen in the exhaust; and 3) A power increase due to densercombustible gasses. The water introduced into the mixing chamber 20needs to be atomised in droplets of a specific size that will be readilyentrained into the air stream passing through the chamber. If the dropsare too large the water will enter the cylinder 2 in liquid form.However, if the drops are too small, they will vaporise or turn intosteam before the fuel mixture within the cylinder has ignited. Thedesign of the mixing chamber 20 allows the water droplets to enter anoptimum velocity air flow to actually supersaturate the air with anamount of water which is greater than 100% relative humidity. In fact,up to 50% more water can be carried in the air with the present chamberconstruction. The atomised water in the fuel mixture helps to cool theengine cylinder whilst increasing power output due to expansion of thewater upon combustion of the fuel in the cylinder.

[0043] In one trial, sufficiently small droplets were produced through a2 micron nozzle. The mixing of these droplets and the ability to retainthem as droplets in the air intake gave far better results than througha 4 micron nozzle for instance. It is envisaged that even smallerdroplets may provide a further increase in the engine performance. Ithas also been found that the addition of 10% methanol in the waterfurther enhances the efficiency of the engine and helps to limit anypre-ignition concerns with the hydrogen gas. Higher amounts of methanolgive higher power output, but there is a financial tradeoff.

[0044] 5. Pressure Control.

[0045] The Venturi intake is shaped to increase density of air whilstalso taking energy out of it, to thereby reduce its temperature.

[0046] 6. Temperature Control.

[0047] The reverse-cycle heat exchanger further reduces the temperatureof the air, if required, in warmer climates, or may be used to increasethe temperature of the air in cooler climates. The optimum temperaturewill depend on the liquid fuel being injected into the engine cylinder.

[0048] 7. Order of Entry of Ingredients into the Mixer.

[0049] Despite the positioning of the water inlet 22, as shown in thedrawings, the greatest advantage may be gained through the mixer if thewater is supplied in the first third of the .mixer to allow for thoroughsaturation of the air intake prior to the addition of the hydrogen gasin the central point of the mixer. This allows the addition of hydrogenand oxygen to be done in a stable controlled environment without therisk of a premature ignition of the two gasses. This allows for anoxygen saturated environment to exist right up to the point of liquidfuel injection into the engines cylinder.

[0050] The entry of the hydrogen and the water saturated intake airslows down the rate of reaction in the cylinder, so we can advance thetiming of the engine without fear of pre-ignition to approximately 40DBTDC. (degrees before top dead centre) This is 20 DBTDC before mostdirect injection engines. This appears to allow more useful work, andmore complete burning of fuel during the power stroke of the engine,because the engine again uses less liquid fuel to perform the same task.

[0051] Apart from the increased engine performance, and associatedreduction in fuel consumption that the addition of hydrogen, oxygen andwater gives the diesel engine, green-house gases produced by an enginefitted with the apparatus have been found to be substantially reducedand indeed a net zero green-house gas output may be achieved when dieselfuel is replaced with canola oil, or the like.

[0052] The above described apparatus has been described with specificreference to application to a compression ignition engine, such as adiesel engine, however it should be appreciated that the apparatus maybe equally applicable to any other form of engine. Further, theapparatus has been described by way of example only and manymodification and variations may be made thereto without departing fromthe spirit and scope of the invention as described.

1. An apparatus for feeding hydrogen into an intake of an engine, including: an air inlet for admitting air to the apparatus; a hydrogen inlet for admitting hydrogen to the apparatus; a mixing chamber for generating a fuel mixture from hydrogen and air introduced from the inlets, the chamber being adapted to couple to the intake of the engine, for introducing the fuel mixture thereto; and control means for controlling airflow through the mixing chamber; wherein the control means is operated to control the velocity of the airflow to supersaturate the air at a level which is up to or greater than about 100% relative humidity thereby and mixing the hydrogen into the airflow increasing the power developed by the engine.
 2. An apparatus as claimed in claim 1, in which the air is supersaturated with an additive or mixture of additives.
 3. An apparatus as claimed in claim 2, in which the additive is water, methanol, or other additive including mixtures thereof.
 4. An apparatus as claimed in claim 3, in which the air is supersaturated with a water and methanol mixture.
 5. An apparatus as claimed in claim 3, in which the air is supersaturated with water.
 6. An apparatus as claimed in any preceding claim, further including an inlet for introducing the additive into the fuel mixture.
 7. An apparatus as claimed in claim 6, in which the inlet is a water inlet for introducing water or a water and methanol mixture.
 8. An apparatus as claimed in claim 7, in which the inlet is for introducing atomised water or a mixture containing water.
 9. An apparatus as claim d in any one of claims 1 to 8, further including a temperature control device for controlling temperature of the air passing through the mixing chamber.
 10. An apparatus as claimed in any one of claims 1 to 9, further including a density control assembly for controlling density of the air entering the mixing chamber.
 11. An apparatus as claimed in claim 10, wherein the density control assembly includes a Venturi intake.
 12. An apparatus as claimed in any one of claims 1 to 11, wherein the control means includes an air volume control.
 13. An apparatus as claimed in claim 12, wherein the air volume control is in the form of a butterfly valve, positioned between the mixing chamber and the air inlet.
 14. A apparatus as claimed in any one of claims 1 to 13, wherein the control means includes an air speed control for varying an effective cross-section of air flow through the apparatus.
 15. An apparatus as claimed in claim 14, wherein the air speed control is in the form of an annular collar arranged in the chamber for radial expansion or contraction.
 16. An apparatus an claimed in claim 15, wherein the collar is in the form of an expandable bladder.
 17. An apparatus as claimed in claim 15 or 16, wherein the chamber includes an annular cage arranged to limit inward expansion of the collar so as to maintain at least a minimum cross-section of the air flow through the chamber.
 18. An apparatus as claimed in any one of claims 1 to 17, including mixing fins to enhance turbulent air flow within the chamber.
 19. An apparatus as claimed in any preceding claim, in which the hydrogen is thoroughly or uniformly mixed into the air flow so that the mixture does not separate into components prior to b ing admitted to the engine.
 20. An apparatus as claimed in any one of claims 1 to 19, further including an electr lysis cell or reformation system, plazma means or other means, for dissociating water into hydrogen and oxygen gas, for introduction into the mixing chamber.
 21. An apparatus according to any one of claims 16 to 20, in which the bladder is inflated during low engine speeds and deflated at high engine speeds.
 22. An apparatus according to any one of claims 1 to 21, in which the optimum velocity of the airflow within the mixing chamber is from 15 to 20 MS⁻¹.
 23. An apparatus according to any one of claims 1 to 22, in which up to 50% more water is carried by the airflow to increase the relative humidity to greater than 100%.
 24. An apparatus according to any one of claims 8 to 23, in which the water is atomised through a 2 micron nozzle.
 25. An apparatus according to any one of claims 3 to 24, in which methanol is added to the water to further increase the efficiency of the engine.
 26. An apparatus according to any one of claims 3 to 25, in which the water is introduced into the first third of the mixing chamber for permitting saturation of the air prior to the addition of hydrogen to the mixing chamber.
 27. An apparatus according to any one of claims 1 to 26, in which the engine having the apparatus can be tuned so that ignition of the engine can be advanced up to 40° DBTDC.
 28. An engine having apparatus as claimed in any one of claims 1 to
 21. 29. An engine according to claim 28, which is a compression ignition engine or a spark ignition engine.
 30. An engine according to claim 29, which is a diesel engine, an internal combustion engine, a petrol engine, a rotary engine, a rankin engine or other type of engine.
 31. An apparatus for feeding hydrogen into an intake of an engine, substantially as hereinbefore described with refer nce to the accompanying drawings.
 32. An engine, substantially as hereinbefore described with refer nce to th accompanying drawings. 